import java.util.Scanner;

public class TestE {
    public static void main(String[] args) {
        int a;
        String t;
        Scanner sc = new Scanner(System.in);
        while (sc.hasNext()){
            a = sc.nextInt();
            //a>100?t="Score is error!":a>=90?t="A":a>=80?t="B":a>=70?t="C":a>=60?t="D":a<=0?t="Score is error!":t="E";
            if (a>100){
                t="Score is error!";
            }else {
                if (a>=90){
                    t="A";
                }else {
                    if (a>=80){
                        t="B";
                    }else {
                        if(a>=70){
                            t="C";
                        }else {
                            if (a>=60){
                                t="D";
                            }else {
                                if (a<=0){
                                    t="Score is error!";
                                }else {
                                    t="E";
                                }
                            }
                        }
                    }
                }

            }
            System.out.println(t);

        }
    }
}
